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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Suspension | Brakes | Chassis > Rotor Thickness



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      08-12-2011, 07:01 PM   #1
skydiver1921
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Rotor Thickness

Took my 08 328i to the dealer for a rotor change. They are telling me that my rear rotors are currently at 19.4 thickness and the minimum thickness is 18.4. Is 1mm thicker not good enough for a change?? Has anyone encountered anything like this... I'm looking for some feedback since it seems pretty bizarre that at 1mm above min they would refuse to change.
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      08-12-2011, 07:44 PM   #2
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Originally Posted by skydiver1921 View Post
Took my 08 328i to the dealer for a rotor change. They are telling me that my rear rotors are currently at 19.4 thickness and the minimum thickness is 18.4. Is 1mm thicker not good enough for a change?? Has anyone encountered anything like this... I'm looking for some feedback since it seems pretty bizarre that at 1mm above min they would refuse to change.
I'm out of warranty (78k miles) and recently had a BMW dealer in Tampa inspect my brakes. My rear back pads had 4mm and the rear rotors were 1mm above spec, which sounds a lot like your situation.

Given this, they recommended that I change the pads ASAP and if I waited too long, I might score the rotors. I asked if the rotors would last very long and they told me they should last long enough to wear through a new set of pads. So, I agreed to get the pads changed.

1mm doesn't sound like much and I'm not an expert so I'd be interested hearing other's opinions. That said, they had a chance to up-sell me on new rotors and they chose not to.
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      08-12-2011, 09:21 PM   #3
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Quote:
Originally Posted by skydiver1921 View Post
Took my 08 328i to the dealer for a rotor change. They are telling me that my rear rotors are currently at 19.4 thickness and the minimum thickness is 18.4. Is 1mm thicker not good enough for a change?? Has anyone encountered anything like this... I'm looking for some feedback since it seems pretty bizarre that at 1mm above min they would refuse to change.
If they specify it down to .4 mm then 1mm is quite a bit. You're good for quite a while.
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      08-12-2011, 11:18 PM   #4
skydiver1921
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Interesting, your Tampa dealership said at 4mm pads needed to be changed. My dealer told me that im currently at 6mm (BMW CPO certification requires all pads under 5mm to be changed) and he said they wouldn't need to be changed normally until 2.5. But your dealer told you to change at 4mm. I was told that a light would come on telling me the brakes needed to be changed when they reached 2.5 thickness, but if at 4mm you're in danger of messing up your rotors then either my dealer is lying or yours is. I wonder which it is 2.5, or 4mm?

I'm starting to wonder if BMW isn't skimping on brake maintenance to lower costs, just like they've done with the 15k oil change and lifetime tranny fluid.
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      08-12-2011, 11:56 PM   #5
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They're all full of shit. Wait for metal on metal.
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      08-13-2011, 12:44 AM   #6
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Quote:
Originally Posted by skydiver1921 View Post
Interesting, your Tampa dealership said at 4mm pads needed to be changed. My dealer told me that im currently at 6mm (BMW CPO certification requires all pads under 5mm to be changed) and he said they wouldn't need to be changed normally until 2.5. But your dealer told you to change at 4mm. I was told that a light would come on telling me the brakes needed to be changed when they reached 2.5 thickness, but if at 4mm you're in danger of messing up your rotors then either my dealer is lying or yours is. I wonder which it is 2.5, or 4mm?

I'm starting to wonder if BMW isn't skimping on brake maintenance to lower costs, just like they've done with the 15k oil change and lifetime tranny fluid.
This thread is about rotors, not pads. BMW specifies a rotor change at 18.4mm. The OP is at 19.4 so he still has a mm left before the dealer will chsnge it under warranty
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      08-13-2011, 06:04 AM   #7
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Originally Posted by mlifxs View Post
I'm out of warranty (78k miles) and recently had a BMW dealer in Tampa inspect my brakes. My rear back pads had 4mm and the rear rotors were 1mm above spec, which sounds a lot like your situation.

Given this, they recommended that I change the pads ASAP and if I waited too long, I might score the rotors. I asked if the rotors would last very long and they told me they should last long enough to wear through a new set of pads. So, I agreed to get the pads changed.

1mm doesn't sound like much and I'm not an expert so I'd be interested hearing other's opinions. That said, they had a chance to up-sell me on new rotors and they chose not to.
Not to jack the thread into a pad discussion, but the car has a brake wear system that indicates when the pads are at minimum spec and need replacement. Why not just wait until the light comes on. You have a few thousand miles after the light comes on to change the pads out.

Regarding rotors and "up selling" you them. Is the dealer going to remove the rotors, put them on a lathe and resurface them? They should. My opinion is the price difference to have the rotors "turned" is about 50% of the price of new rotors, so since the remove and replace labor is the same, why not just get new rotors, and have fresh brakes. Rotor thickness is one thing, but you also need to think about heat cycles. Your used rotors have been heat cycled many times, which affects longevity under use with the new pads. New rotors have not been heat cycled.

And why let a dealer do brakes in the first place? Their labor rates are more expensive than an independent BMW shop. Brake replacement is not rocket science, so why not go to an independent BMW shop, save some cost on labor to offset the price of new rotors (if they were to be added into the job at the dealer).
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      08-13-2011, 12:59 PM   #8
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Quote:
Originally Posted by skydiver1921 View Post
Interesting, your Tampa dealership said at 4mm pads needed to be changed. My dealer told me that im currently at 6mm (BMW CPO certification requires all pads under 5mm to be changed) and he said they wouldn't need to be changed normally until 2.5. But your dealer told you to change at 4mm. I was told that a light would come on telling me the brakes needed to be changed when they reached 2.5 thickness, but if at 4mm you're in danger of messing up your rotors then either my dealer is lying or yours is. I wonder which it is 2.5, or 4mm?

I'm starting to wonder if BMW isn't skimping on brake maintenance to lower costs, just like they've done with the 15k oil change and lifetime tranny fluid.
I don't know. At the time I was thankful to know about the wear level of the pads (my CBS for the rear brakes was still showing 30k miles!). I also had another issue in need of attention so I went ahead with a pad change.

Again, I was surprised about the rotor tolerance but happy not to replace them as it would have doubled the quote for the pads alone.
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      08-13-2011, 01:12 PM   #9
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Quote:
Originally Posted by ENINTY View Post
Not to jack the thread into a pad discussion, but the car has a brake wear system that indicates when the pads are at minimum spec and need replacement. Why not just wait until the light comes on. You have a few thousand miles after the light comes on to change the pads out.

Regarding rotors and "up selling" you them. Is the dealer going to remove the rotors, put them on a lathe and resurface them? They should. My opinion is the price difference to have the rotors "turned" is about 50% of the price of new rotors, so since the remove and replace labor is the same, why not just get new rotors, and have fresh brakes. Rotor thickness is one thing, but you also need to think about heat cycles. Your used rotors have been heat cycled many times, which affects longevity under use with the new pads. New rotors have not been heat cycled.

And why let a dealer do brakes in the first place? Their labor rates are more expensive than an independent BMW shop. Brake replacement is not rocket science, so why not go to an independent BMW shop, save some cost on labor to offset the price of new rotors (if they were to be added into the job at the dealer).
I don't know of anyEuropean brand that allows for "turning" the rotors - either replace them or keep them - there is no lathe involved with Euro rotors.
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      08-13-2011, 01:36 PM   #10
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Quote:
Originally Posted by ENINTY View Post
Not to jack the thread into a pad discussion, but the car has a brake wear system that indicates when the pads are at minimum spec and need replacement. Why not just wait until the light comes on. You have a few thousand miles after the light comes on to change the pads out.

Regarding rotors and "up selling" you them. Is the dealer going to remove the rotors, put them on a lathe and resurface them? They should. My opinion is the price difference to have the rotors "turned" is about 50% of the price of new rotors, so since the remove and replace labor is the same, why not just get new rotors, and have fresh brakes. Rotor thickness is one thing, but you also need to think about heat cycles. Your used rotors have been heat cycled many times, which affects longevity under use with the new pads. New rotors have not been heat cycled.

And why let a dealer do brakes in the first place? Their labor rates are more expensive than an independent BMW shop. Brake replacement is not rocket science, so why not go to an independent BMW shop, save some cost on labor to offset the price of new rotors (if they were to be added into the job at the dealer).
BMW does not resurface rotors. When they sell you them new, they're already at a tight tolerance so using a lathe on them would significantly decrease their life.

If something is wrong with your rotor, theres no fixing it, you should get it replaced.
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